Active matrix type liquid crystal display device having chromium alloy connecting portions at pixel electrode or near driving circuit terminals

ABSTRACT

In an active matrix type liquid crystal display device, at least material of one element, forming the connecting portion between signal transfer lines related to the scan lines and the data signal lines of the device, is an alloy of at least a chemical element selected from the group consisting of Nb, Mo, Ta, and W, with Cr, the scan lines and means for generating scan pulses are connected to each other via a first opening formed in an insulating film, the data signal lines and the means for generating image data are connected to each other via a second opening formed in an insulating film, a polycrystalline thin film, which is connected to the means for generating scan pulses, is inserted into the first opening, and a polycrystalline thin film, which is connected to the means for generating image data, is inserted into the second opening, and the polycrystalline thin film is composed of indium tin oxide, which is made of mainly indium oxide and added tin oxide, having a specific resistance of, at the utmost, 6×10 −4  Ωcm.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid crystal display device, andmore particularly to an active matrix type liquid crystal display deviceusing thin film transistors (TFT).

In an active matrix type liquid crystal display device, a TFT (thin filmtransistor) is used as a semiconductor operating element (switchingelement). An inverted staggered structure is generally used for thestructure of the TFT, wherein gate electrodes are formed on a substrateand signal lines and other electrodes are formed thereon. Practically,scan signal lines (such as gate lines and gate electrodes) are formed ona transparent insulating substrate, a gate insulating layer is formedthereon, a semiconductor layer is formed on the upper portion of thegate insulating layer, drain electrodes (data lines) and sourceelectrodes are formed on the semiconductor layer, and transparent pixelelectrodes are connected to the source electrodes. An image signalvoltage is supplied to the drain electrodes (data lines). A liquidcrystal display device using such a TFT structure is disclosed, forinstance, in JP-A-2-48639 (1990).

When a driving circuit is formed on a periphery of the substrate, any oftwo kinds of mounting methods, such as TCP (Tape Carrier Package) andCOG (Chip On Glass) methods, have been used.

Conventionally, the TCP method has been used more widely than the COGmethod. However, currently, the COG method is becoming to be used morewidely in view of its superiority in cost reduction, finer pitchformation, and other advantages.

In accordance with the COG method, there are three kinds of connections,such as a connection of the input terminal of the driving circuit chipwith the substrate, a connection of the output terminal of the drivingcircuit chip with the substrate, and a connection of the substrate witha FPC (Flexible Printed Cable) which is connected to an externalcircuit. And, an ACF (Anisotropic Conductive Film) is inserted at eachof the above connections so that the connection is established via theACF. In order to ensure reliability of the connection in the above case,an indium tin oxide (ITO) film, which is composed mainly of indium oxideto which tin oxide is added, is used as a wiring material of thesubstrate.

The liquid crystal display device using TFT technology has a featurethat the display quality is superior, because active driving ispossible. However, the process for forming a TFT onto the substrate iscomplex, and at least six separate photolithograpy processes arerequired. The reason for this is that six kinds of fundamental elements(film) are required for constructing the TFT, such as a scan signal line(gate lines), a gate insulating film, a semiconductor layer, a drainelectrode (data line, generally as same as source electrode), atransparent pixel electrode, and a passivation layer, and patterning ofeach of the above films is performed by photolithography. Furthermore,because the thickness of all of the above films is several hundreds nm,and the width of the line formed by the patterning is small, such as inthe order of 10 μm, breakage of the lines (particularly, the data lineand transparent pixel electrode) readily occurs, when they arecontaminated with foreign particles, or at a portion crossing over astep on the base, and, if the patterning is not performed precisely inthe photolithography process, a short circuit between electrodes orlines is readily created. If surface contamination during the process isadded as a further consideration, it is seen that the electrical contactresistance between the source electrode and the transparent pixelelectrode, and the gate line, or the data line, and the transparentpixel electrode at the terminal portion around the substrate, isincreased significantly. Once the above phenomena are generated, defectsin the display of data by the liquid crystal display device result. Thatmeans that the production yield of the substrate is decreased, and theproduction cost is increased.

As one of the conventional methods of increasing the production yield, astructure has been proposed wherein an insulating film between layers(passivation layer) is provided on the source electrode and the drainelectrode of the TFT, and the source electrode and the drain electrodeare connected with the pixel electrode via an opening provided in theinsulating film between layers. In such a structure, a short circuitbetween the source electrode and the drain electrode with the pixelelectrode, which is readily created when these electrodes are formed onthe same plane, can be prevented.

However, in the conventional liquid crystal display device, decreasingthe contact resistance at the connecting portion of each of theelements, which form conductive paths for electrical signals, has notbeen considered thoroughly when mounting the driving circuit, the TFT,and other elements on the substrate of the liquid crystal displaydevice, and, particularly, a problem, such as low production yield ofthe terminal connecting portion, has not been solved. That is, in orderto decrease the contact resistance when the driving circuit chip isconnected with the drain line, the drain line is composed of Cr(chromium), an ITO film is arranged at the surface of the drivingcircuit chip, and the drain line and the driving circuit chip arecontacted all through the surface so as to increase the contact area. Onthe other hand, the area of the region, other than the displaying regionof the display panel (peripheral area), is required to be decreased.However, if the area of the contacting portion is decreased in order tomeet this requirement, the contact resistance can not be decreased,because the specific contact resistance (the contact resistance per unitarea) between ITO and Cr is high. If the area of the contacting portionis increased, water is liable to enter through a defect, such as apin-hole and the like, in the resin used for packaging, and degradationof the contacting portion may readily occur.

SUMMARY OF THE INVENTION

One of the objects of the present invention is to provide an activematrix type liquid crystal display device, which is capable ofdecreasing the contact resistance at the contacting portions betweeneach of the elements forming the conductive paths for signals.

In accordance with the present invention, the active matrix type liquidcrystal display device comprises a liquid crystal layer including aliquid crystal material which forms a plurality of pixels, a pair ofsubstrates, at least one of which is transparent, the substrates beingarranged to face each other while holding the liquid crystal layertherebetween, means for generating scan pulses, means for generatingimage data, a plurality of scan lines, which are arranged dispersedly onone substrate of the pair of substrates and are connected to the meansfor generating scan pulses, and a plurality of data signal lines, whichare arranged so as to intersect with the plurality of scan lines in amanner to form a matrix and are connected to the means for generatingimage data, and further, comprising, in a plurality of display regionssurrounded by the plurality of the scan lines and the plurality of thedate signal lines, transparent pixel electrodes arranged on onesubstrate of the pair of substrates, counter electrodes arranged to facethe transparent pixel electrodes holding the liquid crystal layertherebetween and supplied with a liquid crystal driving voltage, and

an insulating film which covers the respective semiconductor activeelements for driving the pixels connected to the scan lines, the datasignal lines, and the transparent pixel electrodes, the respective scanlines, the respective data signal lines, and the respectivesemiconductor active elements for driving the pixels, wherein

at least the material of one element forming the connecting portion ofthe elements, which compose the signal transfer lines related to thescan lines and the data signal lines, is an alloy of at least a chemicalelement selected from the group consisting of Nb, Mo, Ta, and W, withCr,

the scan lines and the means for generating scan pulses are connected toeach other via a first opening formed in the insulating film, the datasignal lines and the means for generating image data are connected toeach other via a second opening formed in the insulating film, apolycrystalline thin film, which is connected to the means forgenerating scan pulses, is inserted into the first opening, and apolycrystalline thin film, which is connected to the means forgenerating image data, is inserted into the second opening, and thepolycrystalline thin film is composed of indium tin oxide, which is madeof mainly indium oxide and added tin oxide, having a specific resistanceof, at the utmost, 6×10⁻⁴ Ωcm.

Furthermore, in accordance with another feature of the presentinvention, the active matrix type liquid crystal display devicecomprises a liquid crystal layer including a liquid crystal which formsa plurality of pixels, a pair of substrates, at least one of which istransparent, arranged to face each other with the liquid crystal layerinterposed therebetween, means for generating scan pulses, means forgenerating image data, a plurality of scan lines, which are arrangeddispersedly on one substrate of the pair of substrates and connected tothe means for generating scan pulses, and a plurality of data signallines, which are arranged so as to intersect with the plurality of thescan lines in a manner to form a matrix and are connected to the meansfor generating image data, and

further comprising, in a plurality of display regions surrounded by theplurality of the scan lines and the plurality of the data signal lines,transparent pixel electrodes arranged on one substrate of the pair ofsubstrates,

counter electrodes arranged to face the transparent pixel electrodeswith the liquid crystal layer interposed therebetween and supplied witha liquid crystal driving voltage, and

an insulating film which covers respective semiconductor active elementsfor driving the pixels connected to the scan lines, the data signallines, and the transparent pixel electrodes, respective scan lines,respective data signal lines, and respective semiconductor activeelements for driving the pixels, wherein

at least the material of one element of the elements forming theconnecting portion of the elements, which compose the signal transferlines related to the scan lines and the data signal lines, is an alloyof at least a chemical element selected from a group consisting of Nb,Mo, Ta, and W, with chromium (Cr),

the scan lines and the means for generating scan pulses are connectedvie a first opening formed in the insulating film, the data signal linesand the means for generating image data are connected via a secondopening formed in the insulating film, electrodes of the semiconductoractive element for driving a pixel and the transparent pixel electrodesare connected via a third opening formed in the insulating film, apolycrystalline thin film, which is connected to the means forgenerating scan pulses, is inserted into the first opening, apolycrystalline thin film, which is connected to the means forgenerating image data, is inserted into the second opening, and apolycrystalline thin film, which is connected to the transparent pixelelectrodes, is inserted into the third opening, and the polycrystallinethin film is composed of indium tin oxide, which is made of mainlyindium oxide and added tin oxide, having a specific resistance of, atthe utmost, 6×10⁻⁴ Ωcm.

In composing the above liquid crystal display device, the followingfeatures can be added:

(1) The content of the chemical element which forms the alloy film withchromium is in the range from 20 to 80% by weight.

(2) The scan lines and the means for generating scan pulses are formedvia a plurality of the first openings formed along the scan lines, andthe data signal lines and the means for generating image data areconnected to each other via a plurality of the second openings formedalong the data signal lines.

(3) The specific contact resistance of the polycrystalline film and thealloy at respective ones of the first opening, the second opening, andthe third opening is, at the utmost, 1×10⁵ Ω μm².

(4) Scan pulse transmitting lines, which are arranged in other regionsthan the display region on the substrate as lines belonging to the meansfor generating scan pulses and for transmitting the scan pulses, areconnected with other elements by an anisotropic conductive film, imagedata transmitting lines, which are arranged in other regions than thedisplay region on the substrate as lines belonging the means forgenerating image data and transmitting the image data, are connectedwith other elements by the anisotropic conductive film, polycrystallinethin film is formed on the plane of the scan pulse transmitting linesconnecting the other elements and of the image data transmitting linesconnecting the other elements, and the polycrystalline thin film iscomposed of indium tin oxide, which is made of mainly indium oxide andadded tin oxide, having a specific resistance of, at the utmost, 6×10⁻⁴Ωcm.

In accordance with the means described above, the contact resistance atthe connecting portion can be decreased, because at least one element ofthe elements forming the connecting portion of the elements, whichcompose the signal transfer lines, is made of an alloy of at least achemical element selected from a group consisting of Nb, Mo, Ta, and W,with chromium (Cr). Therefore, the production yield of the circuitelements can be improved even if the area of the mounting region of thecircuit element is decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, and advantages of the presentinvention will be understood more clearly from the following detaileddescription when taken with reference to the accompanying drawings,wherein:

FIG. 1 is a schematic cross section of the drain terminal portion of theliquid crystal display device representing an embodiment of the presentinvention;

FIGS. 2A, 2B, 2C, and 2D show respective cross sections of the terminalconnecting portions;

FIG. 3 is a cross section of the TFT element;

FIGS. 4A, 4B, and 4C show respective cross sections of the terminallines;

FIG. 5 is a plan view of the pixel portion of the TFT panel;

FIGS. 6A, 6B, 6C, and 6D show respective cross sections of the drainterminals when the number of photomasks is taken as 5; and

FIGS. 7A and 7B are respective cross sections of the drain terminalsrepresenting another modified example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained withreference to the drawings.

Embodiment 1

FIG. 1 is a schematic cross section of the drain terminal portion of theactive matrix type liquid crystal display device representing a firstembodiment of the present invention. In FIG. 1, a transparent insulatingsubstrate 10 is provided in the form of a flat plate as one of elementswhich make up a display panel. A display region 12 is formed in theregion indicated by an arrow on the transparent insulating substrate 10,and a drain terminal portion 14 is formed at periphery of the substrate.A color filter substrate 18 is formed on the display region 12 of thetransparent insulating substrate 10 via a sealing agent 16, and aplurality of drain lines 20, operating as data signal lines, are formeddispersedly on the transparent insulating substrate 10. A plurality ofscan lines (omitted in the drawing) are formed via an insulating layerso as to intersect with each of the drain lines 20 in a manner to form amatrix, and transparent pixel electrodes, counter electrodes, TFT (thinfilm transistors) operating as semiconductor active elements for drivingthe pixel, and the like, are formed in each of the plural displayregions surrounded by each of the drain lines 20 and signal linescorresponding to each of the pixels. A liquid crystal layer, includingthe liquid crystal material forming the pixel, is formed between thesubstrate 10 and the color substrate 18.

A driving circuit chip 22, terminal lines 24, and FPC (Flexible PrintedCable) 26 are formed by a COG method at the drain terminal portion 14.The driving circuit chip 22 is provided with circuit elements, such as ashift resister and the like, and is composed as an element of the meansfor generating image data. Bumps made of gold are formed at both andportions of the bottom plane of the driving circuit chip 22, so that oneof the bumps is connected to a pad portion 30 of the drain line 20 viathe anisotropic conductive film (ACF) 28, and the other of the bumps isconnected to a pad portion 34 of the terminal line 24 via theanisotropic conductive film (ACF) 32. Plastic grains, which are platedwith nickel and gold sequentially, are dispersed in the anisotropicconductive films 28, 32, so that the bump made of gold and the padportions 30, 34 may be connected by adding pressure and heat between thebump made of gold and the pad portions 30, 34 to collapse the plasticgrains. That means that the anisotropic conductive film 28, 32 isconductive in a direction normal thereto, but insulative in a horizontaldirection. The FPC 26 is connected to an external power source or atiming circuit, and a wiring pattern made of copper formed at the bottomof the FPC 26 is connected to the pad portion 38 of the terminal line 24via the anisotropic conductive film 36. The pad portions 30, 34 and 38are insulated from the atmosphere since a resin for packaging 40 isapplied around the pad portions 30, 34 and 38.

The pad portion 30 is provided with an indium tin oxide film(hereinafter, called as ITO film) 42 and a protective film 44, as shownin FIG. 2A, and the ITO film 42 is connected to the drain line 20 via anopening 45 formed at an end portion of the protective film 44 whichcovers the drain line 20. The drain line 20 is made of an alloy of Crand Mo, as stated later, and the contact resistance at the connectingportion of the element to the element which composes the signal transferlines can be decreased by connecting the drain line 20 made of the alloywith the ITO film 42. An end portion of the ITO film 42 is connected tothe bump of the driving circuit chip 22 via the anisotropic conductivefilm 28. The ITO film 42 is formed with the same material using the sameprocedure as used for the transparent pixel electrode 46, which isformed with the TFT element, as shown in FIG. 3. The TFT element isprovided with a gate electrode 48, a drain electrode 50, and a sourceelectrode 52, which are formed on the transparent insulating substrate10. Gate insulating layer 54 is formed on the gate electrode 48, and anamorphous silicone (a-Si) semiconductor layer 56 is formed on the gateinsulating layer 54. An n⁺.a-Si layer 58, wherein the amorphous siliconeis doped with phosphorus (P) in a high concentration, is formed on theamorphous silicone semiconductor layer 56, and the amorphous siliconesemiconductor layer 56 is connected to the drain electrode 50 and thesource electrode 52 via the n⁺.a-Si layer 58. The drain electrode 50 andthe source electrode 52 are separated by the protective film 44, and thesource electrode 52 is connected with the transparent pixel electrode 46via an opening 60 formed in the protective film 44. When the TFT isoperated by the scan pulse signal applied to the gate electrode 48, thepulse signal by the image data supplied to the drain electrode 50 isapplied to the transparent pixel electrode 46, and an electric field isapplied to the liquid crystal. With the application of the electricfield to the liquid crystal, the transparency of the pixel portion ischanged, and an image corresponding to the image data is displayed.

The pad portions 34, 38 of the terminal line 24 are composed with adouble layered structure, as shown in FIG. 4A, because high frequencysignals, such as timing signals and the like, are input from FPC 26.That is, the terminal line 24 is composed of the alloy film 62, which isformed with the same material and is made by the same procedure as thedrain line 20, and the ITO film 42, which is formed by the sameprocedure as the transparent pixel electrode 46. The alloy film 62 iscomposed of an alloy of Cr and Mo and is formed on the transparentinsulating substrate 10. The alloy film 62 is covered with theprotective film 44. Openings 64, 66 are formed in the protective film 44at both sides of the alloy film 62. A part of the ITO film 42, which islaminated onto the protective film 44, is inserted into the openings 64,66 of the protective film 44, so that the ITO film 42 and the alloy film62 are connected at the openings 64, 66. The ITO film 42 at the opening64 is connected to the bump made of gold of the driving circuit chip 22via the anisotropic conductive film 28, and the ITO film 42 at theopening 66 is connected to the wiring pattern of the FPC 26 via theanisotropic conductive film 36. The contact resistance at the interfacebetween the alloy film 62 and the ITO film 42 can be decreased, becausethe alloy film 62 is composed of an alloy of Cr and Mo. The alloy film62 is connected to the ITO film 42 only via the openings 64, 66, andother portions are covered with the protective film 44. Therefore, entryof water can be double-prevented by applying a resin for packagingaround the terminal lines 24. Because the end portions of the alloy film62 are covered with the protective film 44, and the ITO film 42 isconnected only via the openings 64, 66, whereby an increase in thecontact resistance and the possibility that the terminal line 24 willbreak with generation of a cell reaction (corrosion) between the alloyfilm 62 and the ITO film 42 caused by the entry of water can beprevented, so that the reliability can be improved.

In accordance with the present embodiment, the contact resistance at theconnecting portion of the drain line 20 with the ITO film 42 in thesignal transmitting path for transmitting the image data can bedecreased, because the drain line 20 is formed with an alloy of Cr andMo to connect the drain line 20 and the ITO film 42.

In accordance with the present embodiment, the connecting portion of theelements which make up the signal transmitting path for transmitting theimage date has been explained. However, the same structure as theprevious embodiment can be applied to the connecting portion of theelements which make up the transmitting path for transmitting scanpulses from the means for generating scan pulses. In this case, thecontact resistance of the connecting portion can also be decreased.

Embodiment 2

Hereinafter, a method of manufacturing films which form the drain line20 and the terminal line 24 will be explained.

First, the drain line 20 and the terminal line 24 were deposited using aconventional DC magnetron sputtering apparatus, and then thecharacteristics of the film were evaluated. The evaluation revealed thatthe specific resistance and film stresses in the film could be improvedsignificantly by using an alloy of Cr added with Mo in comparison withthe Cr film which had been widely used as the gate line and the drainline. Furthermore, the contact characteristics of the alloy of Cr addedwith Mo with ITO was evaluated. The evaluation revealed that the contactcharacteristics of the alloy of Cr added with Mo with ITO wassignificantly improved in comparison with the contact characteristics ofCr film with ITO.

In accordance with the above findings, a Cr—Mo alloy film was formed ona plate of non-alkaline borosilicate glass, which was the same size asthe mass production products (370 mm×470 mm×0.7 mm thickness), using acluster type DC magnetron sputtering apparatus which recently has beenwidely used in mass production lines for making the TFT. The Mo contentin the Cr—Mo alloy target was 50% by weight. The target was manufacturedby the steps of mixing Cr powder of 50% by weight and Mo powder of 50%by weight, enclosing the mixture in a can, pressing it with a HIP (HotIsostatic Pressing) method, machining it to form a size of 260 mm×243mm×6 mm, and pasting six of the fabricated sheets onto a backing platemade of copper. The Cr—Mo alloy films were deposited to a thickness of200 nm with a sputtering power of 9.6 kw, using an argon gas pressure of0.4 Pa. The sheet resistance was determined by a four points probemethod, the film thickness was determined by a stylus type profiler, andthe specific resistance was calculated from the above observed values.The film was formed on a Si wafer, the warp of the wafer was determined,and the film stress was calculated from the above observed values. Theobtained results are indicated in Table 1.

TABLE 1 Temperature of the Specific resistance substrate (° C.) (μΩm)Film Stress (MPa)  25 21 600 130 19 400 200 18  0

In order to provide a comparison with the results on the Cr—Mo alloyfilm (Table 1), the same experiment was performed for the conventional100% Cr film, and the results indicated in Table 2 were obtained.

TABLE 2 Temperature of the Specific resistance substrate (° C.) (μΩm)Film Stress (MPa)  25 22 1100 130 21 1000 200 19  900

Table 1 reveals that, when the Cr—Mo alloy film is used, both thespecific resistance and the film stress are decreased in accordance withan increase in the temperature of the substrate, and the film stressbecomes approximately zero (0) at 200° C. of the substrate temperature.

In comparison with the results on the Cr film shown in Table 2, it isrevealed that the Cr—Mo alloy film has a lower specific resistance and asignificantly lower film stress. Further investigation was performed inthe case of a substrate temperature of 130° C., and, although thecharacteristics of the Cr film were not improved, the specificresistance and the film stress of the Cr—Mo alloy film could bedecreased to 18 μΩcm and 180 MPa, respectively, by optimizing thesputtering power and pressure.

In order to observe the structure of the obtained film, the Cr—Mo alloyfilm and the Cr film, both deposited at 200° C., were observed by ascanning electron microscope (SEM). As a result, a domain structurehaving a grain size of approximately 500 nm, which was composed ofsubgrains of 50-100 nm, was observed in the Cr—Mo alloy film. In thedomain structures, each grain of approximately 500 nm in size is assumedto behave as a single crystalline grain. As a result of observing thecross section of the Cr—Mo alloy film, grain boundaries could notobserved clearly. This showed that the large size grains were compacteddensely. Furthermore, the cutting cross section of the film was seen asif it were torn off, meaning that the film was soft, in other words,superior in elasticity. On the contrary, the Cr film had a small grainsize, such as, at the utmost, 50 nm, and the grain boundary could beobserved clearly. Accordingly, it can be concluded that small grainswere compacted coarsely in the Cr film, and the elasticity of the filmwas small.

Embodiment 3

Hereinafter, the patterning characteristics of the Cr-50 wt % Mo alloyfilms, of the type prepared in the embodiment 2, will be explained.

After forming a wiring pattern of resist by photolithography, an etchingprocess was performed using a cerium (IV) nitrate aqueous ammonium 15%solution, which had been used as an etching solution for Cr. A showertype device was used for the etching process.

The cross section of the formed Cr—Mo alloy film pattern was observed bya scanning electron microscope. As a result, it was revealed that, incontrast to the pattern edge of the Cr wiring line which protrudesperpendicularly from the substrate, the pattern of the Cr—Mo alloy filmhas an edge with a tapered shape, and the angle of the taper wasapproximately 50 degrees. Furthermore, a relationship between the angleof taper and the manufacturing process was investigated in detail. Fromthis, it was revealed that the taper was formed depending on the bakingcondition of the photoresist and the jet pressure in the shower etchingprocess, and it was verified that the taper could be well reproduced atthe edge of the wiring pattern by controlling the above conditions. Thereason why the Cr film does not form a tapered shape well is assumed tobe due to the fact that the adhesive force of the Cr film is so strongthat the etching solution can not penetrate the interface between the Crfilm and the photoresist. The tapered shape of the Cr—Mo alloy film isachieved by penetration of the etching solution between the film and theresist and the progress of the etching in a lateral direction (in aperpendicular direction to the film thickness) isotopically.

Embodiment 4

The contact characteristics of the Cr film with the ITO film, and of theCr—Mo alloy film with the ITO film, will be explained hereinafter.

Respective of ones of the Cr film and the Cr—Mo (50% by weight) alloyfilm were deposited onto a cleaned glass plate by a cluster type DCmagnetron sputtering apparatus. In the above cases, the temperature ofthe substrate was 200° C., and the thickness of the film was 200 nm. Thefilm was manufactured to plural wiring patterns by photolithography,wherein the width of the line was 30 μm, and a pad to place a needle formeasurement was provided at the end portion of the line. Both the Crfilm and the Cr—Mo (50% by weight) alloy film were processed by a wetetching method using a cerium (IV) nitrate aqueous ammonia solution.After stripping off the resist, the SiN film was formed onto the metalwiring pattern by a plasma enhanced chemical vapor deposition (CVD)method as an insulating film between wiring layers. In these cases, thetemperature of the substrate was 300° C., and the thickness of the filmwas 350 nm. Then, through-hole patterns were formed in the SiN film onthe metal wiring patterns by photolithography. The through-holes in theSiN film were manufactured by a dry etching method using a CF₄ and O₂mixed gas. After stripping off the resist, the ITO film was deposited bya DC magnetron sputtering method (in this process, a conventionalin-line type apparatus was used).

Then, a case wherein the temperature of the substrate was 200° C. and anAr and O₂ mixed gas was used for the sputtering process, and anothercase wherein the temperature of the substrate was room temperature andan Ar and H₂O mixed gas was used for the sputtering process, werestudied. In the former case, the deposited ITO film has apolycrystalline state (hereinafter, called as p-ITO), and in the lattercase, the ITO film was amorphous (hereinafter, called as a-ITO). In thecase of amorphous ITO, the film finally crystallizes to apolycrystalline ITO film, because the film is heated at the utmost to240° C. in the subsequent process. The thickness of the film in bothcases was 140 nm. Subsequently, patterning of the ITO film was performedby photolithography to prepare patterns for evaluating the contactresistance, wherein the ITO wiring pattern intersected at a right anglewith the metal wiring pattern via a through-hole opening in the SiNfilm. Then, after producing a current flow from Cr to ITO, respectivevalues of voltage drop V at the contact portions of the Cr film with theITO film, and of the Cr—Mo alloy film with the ITO film, was measured bya four points probe method, and the specific contact resistance wascalculated from the observed values. The results are indicated in Table3.

TABLE 3 (Unit: Ωμm²) Cr—Mo Cr p-ITO <1 × 10³   2 × 10⁵ a-ITO 5 × 10⁴ >5× 10⁶  

In accordance with Table 3, it is revealed that, when the Cr—Mo alloyfilm is used as the metal film, the specific contact resistance with theITO film is smaller than the case when the Cr film is used as the metalfilm, regardless of whether the ITO may be polycrystalline or amorphous.As explained later, it was shown that the specific contact resistance atthe pad portions 30, 34, 38 should be smaller than 1×10⁵ Ωμm².Therefore, in the ease of the Cr film, the contact characteristics wereinsufficient.

The above-mentioned contact resistance was found to be dependent on theresistance of the ITO film itself. That is, when the specific resistanceof the ITO film itself is larger than 6×10⁻⁴ Ωcm, the specific contactresistance can not be decreased to a value lower than 1×10⁵ Ωμm², evenif the Cr—Mo alloy film is used. Furthermore, the specific resistance ofthe ITO film itself varies depending on the sputtering conditions. Forinstance, the specific resistance of the p-ITO is increased when the O₂content is excessive, and the specific resistance of the a-ITO isincreased when the H₂O content is excessive. When the amount of H₂Oadded to Ar is less than 2%, the specific contact resistance can bedecreased to a value equal to or less than 1×10⁵ Ωμm².

Embodiment 5

Hereinafter, the composition of the display portion of a liquid crystaldisplay device (TFT-LCD) manufactured using the techniques establishedby the above embodiments will be explained.

FIG. 5 is a schematic plane view of a pixel in the display portion ofthe liquid crystal display device. The structure of the TFT portion ofthe manufactured device is the same as that of FIG. 3, and the drainterminal portion is as same structure as that indicated in FIG. 2 andFIG. 4A. In FIG. 5, the TFT is formed in addition to the pixel electrode46 in the display region surrounded with the drain line 20 and the gateline 68. The source electrode 52 in the TFT and the pixel electrode 46are connected electrically to each other vie a contact hole CN1 openedin the protective film 44. By adopting the above structure, thefollowing advantages can be achieved:

(1) Because the drain line 20 and the pixel electrode 46 are provided inrespectively different layers, the probability that a short circuit willbe created between the drain line and the pixel electrode can bedecreased remarkably, and subsequent failure can be prevented.

(2) Light leakage from an interval between the drain line 20 and thepixel electrode 46 can be prevented by forming a shield layer using thegate electrodes 48, 68 and the pixel electrode 46 to cover the shieldlayer. Accordingly, a black matrix formed on the color filter substrate18, which is facing the transparent insulating substrate 10, can beomitted. The omission of the black matrix makes it possible to suppressa displacement in the alignment of the transparent insulating substrate10 and the color filter substrate 18 and to improve the aperture ratioof the pixel portion.

(3) For the same reason as the above (2), the added capacitance Cadd canbe formed by overlapping the pixel electrode 46 and the gate line 68 ina plane (the other becomes a parasitic capacitance by overlapping thegate line 68 and the source electrode 62). Therefore, the light leakagefrom this portion can be prevented, and the aperture ratio can beimproved.

(4) In the interval between the drain line 20 and the pixel electrode46, the gate insulating layer 54 and the laminated insulating film ofthe gate insulating layer 54 the protective film 44 form a capacitivecoupling via the shielding film 70, as shown in FIG. 5. Therefore, theparasitic capacitance between the above two electrodes can be decreased.

The number of photomasks, when the structure of the present embodimentis adopted, is six including (1) gate electrode, (2) n⁺.a-Si layer58/amorphous silicone semiconductor layer 56, (3) gate insulating layer54, (4) source electrode 52·drain electrode 50, (5) protective film 44,and (6) pixel electrode 46. However, the photomask for the gateinsulating layer can be omitted, and the gate insulating layer can bemanufactured simultaneously using the mask pattern for the protectivefilm. In this case, since the number of the photomasks is decreased to5, an increase in the number of manufactured panels, that is, animprovement of the throughput, can be achieved. The previous explanationwas provided in consideration of the TFT element portion. However, theterminal portion can be manufactured naturally by the same process (noadditional steps is necessary), and this point is one feature of thepresent invention.

The structure of the drain terminal portion 14 of the TFT panel, whichhas been manufactured with five photomasks, is indicated in FIG. 6. Thefeatures of the drain terminal portion 14 indicated in FIG. 6 incomparison with the case using six photomasks are that the gateinsulating layer 54 is located under the drain line 20, and that bothedges of the gate insulating layer 54 and the protective film 44 arealigned in a plane. The above features are based on omitting themanufacturing of the gate insulating layer using a photomask, and thegate insulating layer 54 and the protective film 44 are manufacturedsimultaneously using the same photomask, as explained previously.

In accordance with the method explained above, TFT substrates weremanufactured. As the ITO film 42, the p-ITO film, of which the substratetemperature was 200° C., was used. In order to compare them to eachother, the following three kinds of substrates, ten of each, weremanufactured.

(a) Gate electrode: Cr-50 wt % Mo alloy film/source electrode·drainelectrode: Cr-50 wt % Mo alloy film.

(b) Gate electrode: Cr-50 wt % Mo alloy film/source electrode·drainelectrode: Cr film.

(c) Gate electrode: Cr film/source electrode·drain electrode: Cr-50 wt %Mo alloy film.

All of the above metal films were deposited under the same condition ofsubstrate temperature of 200° C., as described in the embodiment 2. Theetching was performed by the method explained in the embodiment 3.Therefore, the taper shapes were formed around the gate electrodes of(a) and (b), and an approximately perpendicular pattern edge was formedwith the gate electrode of (c). In the course of manufacturing thepanels, when the electrode film of the structure (c) is deposited, atransferring problem, which was assumed to have originated from a warpof the substrate, occurred in the cluster type sputtering apparatus.Breakage of the substrate could be avoided by transferring it carefully,but the process takes a long time. The trouble is based on the highstress in the Cr film and will result in a decrease in the throughputduring mass production. In this point, the advantage of the Cr—Mo alloyfilm is clearly indicated.

The results of investigating the defects in the obtained panels areindicated in Table 4.

TABLE 4 Number of Panels Gate line breakage Drain line breakageStructure occurred occurred (a) 0 1 (b) 0 10  (c) 2 0

In accordance with Table 4, in one panel of structure (a), a breakage ofthe drain line was observed. However, investigation of the panelrevealed that the reason for the breakage was the presence of foreignparticles in the CVD film, and the drain line 20 itself did not have anyproblems. With the structure (b), the breakage of the drain linesoccurred in all the panels. Observation of the cross sectional structureof the element revealed that the breakage of the drain lines made of Croccurred at the portion where the drain line crosses over the gate line.It is assumed that the cause for this is a large stress such asapproximately 1000 MPa, which is generated in the Cr film, the stressbeing a tensile stress. Therefore, the breakage of the line occurred atthe step crossing over portion. With the structure (c), a breakage ofthe gate line was observed in two panels.

The reason for the breakage was investigated, and it was assumed thatmicro defects existed in the glass substrate, that the etching agent wasimpregnated into the defects when etching the Cr lines, and that thebreakage of the Cr occurred. Furthermore, the same defects existed inthe panel using the Cr—Mo alloy line, but since the Cr—Mo alloy had aremarkably larger crystal grain size than the Cr line and the ductilityof the Cr—Mo film was larger than that of the Cr film, the breakage ofthe Cr—Mo alloy line did not occur during the etching process.Furthermore, Table 4 revealed that the breakage of the drain line didnot occur, although the taper shape was not formed around the gate line.In accordance with this observation, the advantage of a wider processmargin can be expected when using the Cr—Mo alloy film for the line.

Then, all of the panels which did not experience any defect, and a partof the panels which did experience defects, were transferred to the LCDmanufacturing process, and LCD devices were manufactured. That is, analignment layer was formed on a counter substrate having the colorfilters and the common transparent electrodes, and the TFT panel,respectively. Subsequently, the surface of the alignment layer wasprocessed by a rubbing treatment, and beads were dispersed onto thesurface of the alignment layer. After applying a sealing agent ontoperipheral portions of the display area of the substrate, the countersubstrate and the TFT panel were adhered together. Then, the adheredbody was cut to form cells, liquid crystal material was injected into aninterval between the substrate and the TFT panel through an inlet, andthe inlet was sealed. Subsequently, a part of the counter substratecorresponding to the terminal portion of the TFT panel was cut off, andthe polarizers were fixed to the surface of the TFT panel. Aftercompleting the LCD device in the manner described above, the displaycharacteristics of the LCD device were examined by installing a backlight. As a result, no spot defects and linear defects, which are causedby lack of pixels, were not observed in the panel where the Cr—Mo alloyfilm was used for the drain line 20, and the panel was confirmed to bein a preferable condition. No spot defect means that the sourceelectrodes 52 and the transparent pixel electrodes 46 are in apreferable contacting condition at the contact holes CN1 (the opening60) shown in FIG. 3 and FIG. 5.

Then, the panel was operated after mounting an external signal circuitusing driving circuit chip 22 and FPC 26 at the terminal portion of thepanel. As a result, it was found that an irregularity of display wasgenerated with the LCD device using a Cr film as the drain line. Thereason for this was studied, and it was revealed that the contact ofITO/Cr at the terminal wiring portion was insufficient, and a highspecific contact resistance at the above portion generated theirregularity of display. Then, using a contact resistance evaluatingelement provided at an outer portion of the panel, a critical value ofthe specific contact resistance for generating the irregularity ofdisplay was determined. As a result, it was revealed that theirregularity of display did not occur if the specific contact resistancewas smaller than approximately 1×10⁵ Ωμm². When the Cr—Mo alloy film wasused as the lines, the irregularity of display was not generated at all.

After evaluating the panel, the panel was subjected to a hightemperature and high humidity test for confirming its reliability. Itwas confirmed in this test that the panels using the Cr—Mo alloy film asthe lines were not all deteriorated in display quality.

A modified example of the terminal portion structure is indicated inFIG. 7. In accordance with the structure shown in FIG. 7, the drainlines 20 and the ITO film 42 are bonded at almost all the surface,except for the respective end portions of the drain lines 20 which werecovered with the passivation film 44. By adopting the above structure,even if water has entered and reached the surface of the ITO film 42from outside through the resin for packaging, the intrusion of water tothe interface between the ITO film 42 and the drain lines 20 can besuppressed.

In order to obtain the advantages of the present invention, it isessential to decrease the contact resistance at the connecting portionby using Cr—Mo alloy as the material for one of the connecting elementswhich make up the signal transmission paths. Therefore, as anothermodified example, even if the gate line and/or drain line are composedof a laminated film, and the alloy of the present invention is appliedto only the uppermost layer of the laminated layer, in other words, toonly the surface of the opening, the advantages of the present inventioncan be achieved. Practically, it was confirmed that if the uppermostCr—Mo alloy layer of the laminated layer was formed with a filmthickness of at least 20 nm, the contact resistance was decreased, andthe advantages of the present invention could be achieved. As describedlater, the specific contact resistance at the connecting portion can bedecreased to 1×10⁵ Ωμm² by using an alloy composed of at least achemical element selected from the group consisting of Nb, Mo, Ta, andW, and Cr, instead of the Cr—Mo alloy.

The reason why the Cr—Mo alloy film has a remarkably low contactresistance in comparison with the Cr film is assumed to be that, inaccordance with the result of a study of the film surface with aphotoelectron spectroscope, the thickness of an oxide film generated onthe surface of the Cr—Mo alloy film is thinner than that on the surfaceof the Cr film, and the structure of the oxide film differs from that onthe surface of the Cr film.

As explained above, a high production yield can be obtained in both themanufacturing process and the reliability tests by using the Cr—Mo alloyfilm as the line film of the TFT panel, and accordingly, a decrease inthe production cost of the liquid crystal display device can beattained.

Embodiment 6

Hereinafter, the applications of film made of metals other than Cr—Moalloy will be explained.

In order to use an alloy film made of metals other then Cr—Mo alloy, thealloy film was manufactured by adding Nb, Ta, and W, respectively, to Crby 5, 10, 20, 30, and 50% by weight, and the specific resistance andfilm stress of these alloy films was evaluated.

The method of manufacturing these alloys was the same as the methoddescribed in embodiment 2. In accordance with the results measured forthese alloys, the film stress of the Cr—Nb alloy showed almost the sametrend as the Cr—Mo alloy which was explained previously in embodiment 2.In the cases of the Cr—Ta alloy and the Cr—W alloy, a decrease of thestress could be observed from a smaller amount of the additives, namely,approximately 10% by weight as compared to the case of Cr—Mo alloy.Therefore, it can be concluded that the same advantages as the Cr—Moalloy film can be obtained by forming alloys from any of the chemicalelements described above with Cr. Regarding the specific resistance, itwas found that any alloy film made of Cr—Nb, Cr—Ta, and Cr—W,respectively, in the present embodiment had a slightly higher specificresistance than the Cr—Mo alloy film. Therefore, it can be concludedthat, although each of Nb, Ta, and W is remarkably effective as achemical element to form an alloy film with Cr, the Cr—Mo alloy is mostsuperior in comparison with the other alloys in consideration of bothfilm stress and specific resistance.

Although the content of Mo in the Cr—Mo-alloy film in the foregoingdescription is mainly 50% by weight, the Cr—Mo alloy, of which the Mocontent is in a range as wide as from 20 to 80% by weight, can be usedin order to decrease the specific contact resistance. However, byincreasing the Mo content, the etching rate using cerium (IV) nitrateaqueous ammonium solution is decreased, and by decreasing the Mocontent, the film stress is increased. Therefore, the Mo content ispreferably in the range of 30-55% by weight.

As explained above, in accordance with the present invention, thecontact resistance at the connecting portion can be decreased bycomposing the material of the one of the connecting elements composingthe signal transfer lines with an alloy made of a chemical elementselected from the group consisting of Nb, Mo, Ta, and W, with Cr, andaccordingly, the present invention can contribute to an improvement inthe production yield.

What is claimed is:
 1. An active matrix type liquid crystal displaydevice comprising: a pair of substrates, at least one of which istransparent; a liquid crystal layer interposed between said pair ofsubstrates; means for generating scan pulses; means for generating imagedata; a plurality of scan lines, which are arranged dispersedly on onesubstrate of the pair of substrates and are connected to the means forgenerating scan pulses; and a plurality of data signal lines, which arearranged so as to cross with the plurality of the scan lines in a mannerto form a matrix and are connected to the means for generating imagedata; and further, comprising, in a plurality of pixels surrounded bythe plurality of the scan lines and the plurality of the data signallines: transparent pixel electrodes arranged on one substrate of thepair of substrates, counter electrodes arranged to face the transparentpixel electrodes with the liquid crystal layer being held between themand supplied with a liquid crystal driving voltage, and an insulatingfilm which covers respective semiconductor active elements for drivingthe pixels connected to the scan lines, the data signal lines, and thetransparent pixel electrodes, respective scan lines, and respective datasignal lines; wherein material forming portions connecting the scanlines with the means for generating scan pulses, and connecting the datasignal lines with the means for generating image data, a substantiallysimilar composition which is an alloy of Cr containing at least achemical element selected from the group consisting of Nb, Mo, Ta and W,and wherein the scan lines and the means for generating scan pulses areconnected to each other via a first opening formed in the insulatingfilm, the data signal lines and the means for generating image data areconnected to each other via a second opening formed in the insulatingfilm, a polycrystalline thin film, which is connected to the means forgenerating scan pulses, is inserted into the first opening, and apolycrystalline thin film, which is connected to the means forgenerating image data, is inserted into the second opening, and thepolycrystalline thin film is composed of indium tin oxide, which is madeof mainly indium oxide and added tin oxide, having a specific resistanceof, at the utmost, 6×10⁻⁴ Ωcm.
 2. The active matrix type liquid crystaldisplay device as claimed in claim 1, wherein said scan lines and saidmeans for generating scan pulses are connected via plural first openingsformed along said scan lines, and said data signal lines and said meansfor generating image data are connected to each other via plural secondopenings formed along said data signal lines.
 3. The active matrix typeliquid crystal display device as claimed in claim 1, wherein a specificcontact resistance of the polycrystalline thin film with the alloy atthe first opening and the second opening is at the utmost, 1×10⁵ Ω μm².4. The active matrix type liquid crystal display device as claimed inclaim 1, wherein the the chemical element which forms an alloy with Cris in the range of 20˜80% by weight.
 5. The active matrix type liquidcrystal display device as claimed in claim 1, wherein lines fortransmitting scan pulses, which are arranged on the substrate outsidethe pixels as lines belonging to the means for generating scan pulsesand transmitting the scan pulses are connected to first members via ananisotropically conductive film; lines for transmitting image data,which are arranged on the substrate outside the pixels as linesbelonging to the means for generating image data and transmitting theimage data are connected to second members via an anisotropicallyconductive film; a polycrystalline thin film is formed at the connectedplane of said lines for transmitting scan pulses with the first membersand at the connected plane of said lines for transmitting image datawith the second members, respectively; and said polycrystalline thinfilm is composed of indium tin oxide, which is made of mainly indiumoxide and added tin oxide, having a specific resistance of, at theutmost, 6×10⁻⁴ Ωcm.
 6. The active matrix type liquid crystal displaydevice as claimed in claim 1, wherein at least one of the scan lines andthe data signal lines is formed at other than the connecting portionsthereof of a material other than the material of the connection portionsthereof.
 7. A liquid crystal display apparatus as claimed in claim 6,wherein said polycrystalline film is composed of ITO comprising indiumoxide as a main component and tin oxide as an additive.
 8. A liquidcrystal display apparatus as claimed in claim 6, wherein saidpolycrystalline film, which forms a part of said signal line, is formedon said Cr—Mo alloy film at said connecting portion.
 9. A liquid crystaldisplay apparatus as claimed in claim 6, wherein a specific contactresistance between said polycrystalline film and said Cr—Mo alloy filmis equal to or less than 1×10⁵ Ωcm².
 10. An active matrix type liquidcrystal display device comprising: a pair of substrates, at least one ofwhich is transparent; a liquid crystal layer interposed between saidpair of substrates; means for generating scan pulses; means forgenerating image data; a plurality of scan lines, which are arrangeddispersedly on one substrate of the pair of substrates and are connectedto the means for generating scan pulses; and a plurality of data signallines, which are arranged so as to cross with the plurality of the scanlines in a manner to form a matrix and are connected to the means forgenerating image data; and further, comprising, in a plurality of pixelssurrounded by the plurality of the scan lines and the plurality of thedata signal lines: transparent pixel electrodes arranged on onesubstrate of the pair of substrates, counter electrodes arranged to facethe transparent pixel electrodes with the liquid crystal layer beingheld between and supplied with a liquid crystal driving voltage, and aninsulating film which covers respective semiconductor active elementsfor driving the pixels connected to the scan lines, the data signallines, and the transparent pixel electrodes, respective scan lines, andrespective data signal lines; wherein materials forming at least oneportion connecting said scan lines with the means for generating scanpulses, at least one portion connecting the data signal lines with themeans for generating image data, and at least one portion connectingelectrodes composing said semiconductor active elements for drivingpixels with the transparent pixel electrodes, the materials having asimilar composition which is an alloy of Cr containing at least achemical element selected from the group consisting of Nb, Mo, Ta and W;the scan lines and the means for generating scan pulses are connected toeach other via a first opening formed in the insulating film, the datasignal lines and the means for generating image data are connected toeach other via a second opening formed in the insulating film, theelectrodes of the semiconductor active element for driving pixels andthe transparent pixel electrodes are connected to each other via a thirdopening formed in the insulating film, a polycrystalline thin film,which is connected to the means for generating scan pulses, is insertedinto the first opening, a polycrystalline thin film, which is connectedto the means for generating image data, is inserted into the secondopening, a polycrystalline thin film, which is connected to thetransparent pixel electrodes, is inserted into the third opening, andthe polycrystalline thin film is composed of indium tin oxide, which ismade of mainly indium oxide and added tin oxide, having a specificresistance of, at the utmost, 6×10⁻⁴ Ωcm.
 11. The active matrix typeliquid crystal display device as claimed in claim 10, wherein said scanlines and said means for generating scan pulses are connected via pluralfirst openings formed along said scan lines, and said data signal linesand said means for generating image data are connected to each other viaplural second openings formed along said data signal lines.
 12. Theactive matrix type liquid crystal display device as claimed in claim 10,wherein a specific contact resistance of the polycrystalline thin filmwith the alloy at the first opening and the second opening is, at theutmost, 1×10⁵ Ω μm².
 13. The active matrix type liquid crystal displaydevice as claimed in claim 10, wherein a specific contact resistance ofthe polycrystalline thin film with the alloy at the first opening, thesecond opening, and the third opening is, at the utmost, 1×10⁵ Ω μm².14. The active matrix type liquid crystal display device as claimed inclaim 10, wherein the the chemical element which forms an alloy with Cris in the range of 20˜80% by weight.
 15. The active matrix type liquidcrystal display device as claimed in claim 10, wherein lines fortransmitting scan pulses, which are arranged on the substrate outsidethe pixels as lines belonging to the means for generating scan pulsesand transmitting the scan pulses are connected to first members via ananisotropically conductive film; lines for transmitting image data,which are arranged on the substrate outside the pixels as linesbelonging to the means for generating image data and transmitting theimage data are connected to second members via an anisotropicallyconductive film; a polycrystalline thin film is formed at the connectedplane of said lines for transmitting scan purses with the first membersand at the connected plane of said lines for transmitting image datewith the second members, respectively; and said polycrystalline thinfilm is composed of indium tin oxide, which is made of mainly indiumoxide and added tin oxide, having a specific resistance of, at theutmost, 6×10⁻⁴ Ωcm.
 16. The active matrix type liquid crystal displaydevice as claimed in claim 10, wherein at least one of the scan linesand the data signal lines is formed at other than the connectingportions thereof of a material other than the material of the connectionportions thereof.
 17. A liquid crystal display apparatus as claimed inclaim 16, wherein said ITO has a specific resistance equal to or lessthan 6×10⁻⁴ Ωcm.
 18. An active matrix type liquid crystal display devicecomprising: a pair of substrates, at least one of which is transparent;a liquid crystal layer interposed between said pair of substrates; meansfor generating scan pulses; means for generating image data; a pluralityof scan lines, which are arranged dispersedly on one substrate of thepair of substrates and are connected to the means for generating scanpulses; and a plurality of data signal lines, which are arranged so asto cross with the plurality of the scan lines in a manner to form amatrix and are connected to the means for generating image data; andfurther, comprising, in a plurality of pixels surrounded by theplurality of the scan lines and the plurality of the data signal lines:a pair of electrodes including a pixel electrode and a counterelectrode; an insulating film which covers respective semiconductoractive elements for driving the pixels connected to the scan lines, thedata signal lines, and the pixel electrode, respective scan lines, andrespective data signal lines; and material forming portions connectingthe scan lines with the means for generating scan pulses, and connectingthe data signal lines with the means for generating image data, thematerial having a substantially similar composition which is an alloy ofCr containing at least a chemical element selected from the groupconsisting of Nb, Mo, Ta and W; and wherein the scan lines and the meansfor generating scan pulses are connected to each other via a firstopening formed in the insulating film, the data signal lines and themeans for generating image data are connected to each other via a secondopening formed in the insulating film, a polycrystalline thin film,which is connected to the means for generating scan pulses, is insertedinto the first opening, and a polycrystalline thin film, which isconnected to the means for generating image data, is inserted into thesecond opening, and the polycrystalline thin film is composed of indiumtin oxide, which is made of mainly indium oxide and added tin oxide,having a specific resistance of, at the utmost, 6×10⁻⁴ Ωcm.
 19. Theactive matrix type liquid crystal display device as claimed in claim 18,wherein at least one of the scan lines and the data signal lines isformed at other than the connecting portions thereof of a material otherthan the material of the connection portions thereof.
 20. A liquidcrystal display apparatus comprising a structure, wherein: Cr—Mo alloyfilm is formed at portions connecting source electrodes of transistorswith one end of a transparent pixel electrode which is composed ofpolycrystalline film; and a signal line which is composed ofpolycrystalline film is connected with driving circuit chips arranged ona substrate via an anisotropic conductive film.
 21. A liquid crystaldisplay apparatus comprising a pair of substrates, a liquid crystallayer interposed between the pair of substrates, and at leasttransistors, transparent pixel electrodes, signal lines and drivingcircuit chips being provided on at least one of the pair of substrates,wherein: a Cr—Mo alloy film is formed at portions connecting sourceelectrodes of the transistors with one end of one of the transparentpixel electrodes which is composed of polycrystalline film; and a signalline which is composed of polycrystalline film is connected with thedriving circuit chips which are arranged on one of the pair ofsubstrates via an anisotropic conductive film.
 22. A liquid crystaldisplay apparatus comprising a structure, wherein: Cr—Mo alloy film isformed at portions connecting source electrodes of transistors with oneend of a transparent pixel electrode which is composed ofpolycrystalline film and at portions connecting signal electrodes withone end of a data signal line which is composed of polycrystalline film;and a signal line which is composed of polycrystalline film is connectedwith driving circuit chips arranged on a substrate via an anisotropicconductive film.
 23. A liquid crystal display apparatus comprising astructure, wherein: Cr—Mo alloy film is formed at portions connectingsource electrodes of transistors with one end of a transparent pixelelectrode which is composed of polycrystalline film and at portionsconnecting signal electrodes with one end of a scan line which iscomposed of polycrystalline film; and a scan line which is composed ofpolycrystalline film is connected with driving circuit chips arranged ona substrate via an anisotropic conductive film.